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Ok finally bit the bullet and ordered some Parks 50 form Kelly Cupples. I know i can quench all simple steels 10xx series but what about damascus? its mainly 1080 and 15n20 or 1095 and 15n20. im guessing it should be fine for this too. so my real question is what cant/ shouldnt i quench in P50?

In a nutshell, you will want to quench the shallow hardening steels in P50. Those that require a quick transition through the pearlite 'window'. Everything you mention will qualify.

The deeper hardening steels like O1, L6, 5160, 52100, etc., that do not require quick extraction of heat for optimum martensite creation can use slower oils.

7 to 10 second oils: Parks #50, Houghto-Quench “K” (and perhaps DT 49, but I haven’t tested it yet)

Steels: 1070, 1075, 1080, 1084, 1095, W-1, W-2, 15n20

11 to 13 second oils: Parks AAA, McMaster Carr, Hougto-quench “G”, Chevron 70, Texaco Quenchtex, Gulf Superquench, (and a few others I am forgetting)

Steels: O-1, L-6, 5160, 8670M, 52100, S5, 80CRV2, O-2, or anything else with over .3% Cr or .8% Mn.

Fast quench oils were an industrial afterthought since the shallow hardening steels were from a time of water hardening. To obtain deeper hardening in intricately shaped parts industry created alloys that could handle a slower quench by suppressing pearlite formation (Cr and Mn being the two quickest ways), and so industry moved on with oil quenching and simply left water hardening steels behind. But some niche markets still liked the old carbon steels (like knifemakers) and so some quenchant makers designed some specialty oils that could mimic the speed of water without the nasty effects that cracked and warped steel. Industry is now moving forward again and due to health and air standards are dropping the old oil hardeners in favor of air hardening alloys- just heat it up and let it cool in the air. Believe it or not, in a few more years O-1 will be as obsolete and maybe even as scarce as W2.

Thanks Karl, thats what i figured just wondering if i had only one oil what i absolutely couldn't or shouldn't quench in p50. i understand that the deeper steels dont need to quench too fast but can they or will they crack?

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7 to 10 second oils: Parks #50, Houghto-Quench “K” (and perhaps DT 49, but I haven’t tested it yet)

Steels: 1070, 1075, 1080, 1084, 1095, W-1, W-2, 15n20

11 to 13 second oils: Parks AAA, McMaster Carr, Hougto-quench “G”, Chevron 70, Texaco Quenchtex, Gulf Superquench, (and a few others I am forgetting)

Steels: O-1, L-6, 5160, 8670M, 52100, S5, 80CRV2, O-2, or anything else with over .3% Cr or .8% Mn.

Fast quench oils were an industrial afterthought since the shallow hardening steels were from a time of water hardening. To obtain deeper hardening in intricately shaped parts industry created alloys that could handle a slower quench by suppressing pearlite formation (Cr and Mn being the two quickest ways), and so industry moved on with oil quenching and simply left water hardening steels behind. But some niche markets still liked the old carbon steels (like knifemakers) and so some quenchant makers designed some specialty oils that could mimic the speed of water without the nasty effects that cracked and warped steel. Industry is now moving forward again and due to health and air standards are dropping the old oil hardeners in favor of air hardening alloys- just heat it up and let it cool in the air. Believe it or not, in a few more years O-1 will be as obsolete and maybe even as scarce as W2.

Kevin, Thanks so much for the detailed response. im upgrading for canola oil (which seemed to work for everything) i have been using simple 1080/15n20 mix and 1095/15n20 mix and 1095 mono steel and i probably will continue to use these steels for 90% of my work. so im sure P50 will do well there. But i also work as a manual machinist/ tool and die maker. i use lots of different tool steels but i mostly send my air hardening steels out but i have been heat treating my own scrap cutting dies out of 01. id also like to try some different 52100 san mai or just 52100 knives. i understand that P50 is fast but is it too fast for 01,5160,& 52100? or is it just faster then they need. can they handle that speed or will i see critical errors? when starting out i quenched OTS (5160) in water some times it worked and sometimes it just snapped.

since i know you experiment with metal and probably try everything, a better question to ask?! what is the deepest hardening (slowest) steel you have tried in P50?

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Kevin, Thanks so much for the detailed response. im upgrading for canola oil (which seemed to work for everything) i have been using simple 1080/15n20 mix and 1095/15n20 mix and 1095 mono steel and i probably will continue to use these steels for 90% of my work. so im sure P50 will do well there. But i also work as a manual machinist/ tool and die maker. i use lots of different tool steels but i mostly send my air hardening steels out but i have been heat treating my own scrap cutting dies out of 01. id also like to try some different 52100 san mai or just 52100 knives. i understand that P50 is fast but is it too fast for 01,5160,& 52100? or is it just faster then they need. can they handle that speed or will i see critical errors? when starting out i quenched OTS (5160) in water some times it worked and sometimes it just snapped.

since i know you experiment with metal and probably try everything, a better question to ask?! what is the deepest hardening (slowest) steel you have tried in P50?

For metallurgical research I have quenched most steels in Parks #50 in order to insure homogenous structure, but in that case I don’t care about distortion or micro-fracturing, and very often observe micro-fracturing on alloyed steel that has been fast quenched and left hard. For my blades I am always careful to use the quenchant that matches the optimum cooling curve for my steel. Can you quench O-1 in Parks #50 without cracking? Yes you can, but you can also probably sleep with a dozen rattle snakes in your bedroom and still wake up in the morning… until the morning you don’t.

I have seen plenty of cracks in O-1 from Parks #50, but never from Parks AAA or any of the medium speed oils made for that alloy. When you overkill on quench speed for a given alloy you will naturally have a higher rate of cracking and distortion.

The oils are measured in seconds. This designation comes from the nickel ball test which measures the time it takes the oils to cool a 22mm nickel ball from 1625F to its Currie point of 675F. when the magnet will stick to it again. Parks #50 has been measured from 7 to 10 seconds, while the medium speed oils take from 11 to 14 seconds to cool a 7/8” ball from 1625F to 675F. Pearlite forms at around 1,100F to 1,000F and upper bainite forms in the 800F to 600F range, neither structures are at all desirable in a knife blade. So it is important to quench any steel below 600F within the 10 seconds required for an effective quench. At around a 10 second count Parks #50 will have you around the Ms point (400-450F) where you need to be for the desired results but also to avoid the 375F flash point of that oil; with the speed to get out of the pearlite zone in the process. An 11 second oil will take 11 seconds to reach 675F and then proceed a little more gently from there but the timing is critical for both oils.

You have an investment in the Parks #50, to protect it and keep it working well for you it is important to keep it clean and avoid oxidizing or overheating it. Canola has a higher flash point than Parks #50 but the latter has a well suppressed vapor formation. It is important to keep hot steel entirely under the surface until it is cool enough not to flash the oil, if that happens you are damaging your investment. As I mentioned before, at least 7 seconds to avoid unwanted phases as well as a temperature well above the flash point. With the other steels with more chromium pearlite is suppressed a bit and thus the oil can take 11 to 14 seconds to cool to below the danger zone.

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For metallurgical research I have quenched most steels in Parks #50 in order to insure homogenous structure, but in that case I don’t care about distortion or micro-fracturing, and very often observe micro-fracturing on alloyed steel that has been fast quenched and left hard. For my blades I am always careful to use the quenchant that matches the optimum cooling curve for my steel. Can you quench O-1 in Parks #50 without cracking? Yes you can, but you can also probably sleep with a dozen rattle snakes in your bedroom and still wake up in the morning… until the morning you don’t.

I have seen plenty of cracks in O-1 from Parks #50, but never from Parks AAA or any of the medium speed oils made for that alloy. When you overkill on quench speed for a given alloy you will naturally have a higher rate of cracking and distortion.

The oils are measured in seconds. This designation comes from the nickel ball test which measures the time it takes the oils to cool a 22mm nickel ball from 1625F to its Currie point of 675F. when the magnet will stick to it again. Parks #50 has been measured from 7 to 10 seconds, while the medium speed oils take from 11 to 14 seconds to cool a 7/8” ball from 1625F to 675F. Pearlite forms at around 1,100F to 1,000F and upper bainite forms in the 800F to 600F range, neither structures are at all desirable in a knife blade. So it is important to quench any steel below 600F within the 10 seconds required for an effective quench. At around a 10 second count Parks #50 will have you around the Ms point (400-450F) where you need to be for the desired results but also to avoid the 375F flash point of that oil; with the speed to get out of the pearlite zone in the process. An 11 second oil will take 11 seconds to reach 675F and then proceed a little more gently from there but the timing is critical for both oils.

You have an investment in the Parks #50, to protect it and keep it working well for you it is important to keep it clean and avoid oxidizing or overheating it. Canola has a higher flash point than Parks #50 but the latter has a well suppressed vapor formation. It is important to keep hot steel entirely under the surface until it is cool enough not to flash the oil, if that happens you are damaging your investment. As I mentioned before, at least 7 seconds to avoid unwanted phases as well as a temperature well above the flash point. With the other steels with more chromium pearlite is suppressed a bit and thus the oil can take 11 to 14 seconds to cool to below the danger zone.

Thanks so much for the detailed explanation. i dont pretend to totally understand what is happening during these phase transitions. but i like to know WHY, actually i have a horrible memory and need to understand things in order to really remember them.

i LOVE your rattlesnake analogy!

I will head your advice and protect my quenchant investment.

in actuality i mainly work with simple 10xx steels so P50 should be a good fit.